1,720,968 research outputs found
UWB and mmWaves Communication Techniques and Systems for Healthcare
No full textTelemedicine has been around for decades, and some apparatuses are currently in operation in few hospitals. Relying on advanced wireless technologies, which enable the use of pervasive communications for a variety of different applications, new-generation systems for healthcare become non-invasive, broadband and mobile. High-data rate wireless systems allow users to share huge amounts of data and multimedia content with other users or with service providers. Consequently, the range of potential applications of healthcare assistance expands to include new scenarios that involve very high data rate wireless transmissions like, for instance, seamless exchange of multimedia content. In this chapter, a survey of new-generation wireless communication techniques and systems based on ultra-wideband technology and millimetre-waves radios is provided, with reference to the modern concepts of patient-centric and hospital-centric application scenarios. The opportunities offered by these two broadband wireless communications technologies beyond basic data transfer are highlighted and discussed in the framework of the new application scenarios that these technologies open
Modulation and Detection Strategies for 60 GHz UWB High-Data Rate Wireless Indoor Communications
No full text60 GHz mmWaves radios nowadays are considered as a core short-range wireless technology capable to solve the spectrum shortage due to the exponentially increasing number of wireless users and QoS sensitive multimedia and home entertainment applications. Although there are several published standards, the 60 GHz wireless developmental field is still open as the behavior of the channel is not well studied along the whole available bandwidth - at different carrier frequencies, and also, there is scarcity of research evaluating different transmission technologies besides the standard-defined OFDM and SC-FDE. In this paper, by carefully realized realistic application scenarios, we comparatively analyze the performance of different modulation and detection schemes, using experimental channel impulse responses recorded through an indoor measurement campaign in eight sub-bands from 54 to 66 GHz at several distances in two typical environments: office and residential. The measurements allow us to evaluate the impact of changes in multipath profiles, due to both frequency and surrounding environment, on the bit error rate performance of 60 GHz impulse radio (IR)-UWB signaling, i.e. pulse position modulation (PPM) and pulse amplitude modulation (PAM), and conventional quadrature amplitude modulation (QAM), comparing the performance of different schemes of Rake detection (partial and selective) in modern residential and office environments. The impact of the carrier frequency and the surrounding environment on the achievable performance is also discussed. The results obtained in this study show that different low-complexity Rake receiver architectures are valuable candidates for the future 60 GHz WPANs and WLANs transceivers
A statistical model for the shadowing induced by human bodies in the proximity of a mmWaves radio link
Full text link5G technology is a broad concept that describes the envisaged disruptive evolution of communication technology in the near future, with a dramatic increase in the network data-rate and capacity to support a variety of innovative services. The exploitation of the new spectrum available at mmWaves represents a key enabler for 5G. mmWaves are expected to revolutionize the indoor wireless connectivity providing a very large capacity at very high data rates. It is well known that mmWaves radio links are strongly influenced by human bodies and this issue is very relevant in indoor environments. Several models are available for ray-tracing investigations and line-of-sight blockage, whereas statistical models enabling tractable analytical studies and simulations of mmWaves wireless systems, accounting for people in the link's proximity, are still lacking. In this paper, measurements of 60 GHz channel impulse responses in static but “evolutionary” office scenarios that involve one, two and three individuals are presented. Regression fits are applied to the experimental responses to obtain an accurate characterization of human-induced shadowing events in both proximity and blockage situations. Tractable statistical models are provided for different scenarios and for eight carrier frequencies spanning the bands from 54 to 59 GHz and from 61 to 66 GHz
Performance evaluation of UWB signaling at mmWaves
No full textUltra-wideband (UWB) radios have the potential to achieve very high data rates. However, the coverage is limited over very short ranges, due to the tight limits imposed to the allowed transmission power by the worldwide spectrum regulation at microWaves. Recently, a very large bandwidth has been made available by worldwide regulation at mmWaves. Wide consensus is achieved on the future utilization of the spectral region around 60 GHz for multi-Gbps wireless LAN connectivity. Given the availability of a very large band, up to 7 GHz, mmWaves appear as the natural candidate for UWB transmissions. The aim of this paper is to evaluate the performance of impulse radio (IR)-UWB signalling when operating at mmWaves, i.e., around 60 GHz. The analysis is based on a semi-analytical approach, where the bit error rate (BER) for pulse position modulation (PPM) and pulse amplitude modulation (PAM) is analytically computed and averaged over the empirical probability density function of the signal-to-noise-ratio (SNR) as obtained from a significant set of experimental impulse responses of the UWB indoor channel at mmWaves. These channel impulse responses have been collected through a measurement campaign in a modern office building at eight carrier frequencies spanning the band from 54 to 59 GHz and from 61 to 66 GHz. The results show a promising potential for mmWaves UWB radios
BER of IEEE 802.11ad OFDM radios vs. carrier frequency in real 60 GHz indoor channels
Full text linkMulti-gigabit 60 GHz radios are expected to match QoS requirements of modern multimedia applications. Several published standards were defined based on performance evaluations over standard channel models. Unfortunately, those models, and most models available in the literature, do not take into account the behavior of 60 GHz channels at different carrier frequencies, thus no guidelines are provided for the selection of the best suitable frequency band for a given service. This paper analyzes the impact of changes in multipath profiles, due to both frequency and distance, on the BER performance achieved by IEEE 802.11ad 60 GHz radios. Our analysis is based on real experimental channel impulse responses recorded through an indoor measurement campaign in seven sub-bands from 54 to 65 GHz with a break at 60 GHz at distances from 1 to 5 m. The small-scale fading is modeled by Rician distributions with K-factors extracted from experimental data, which are shown to give good agreement with the empirical distributions. A strong dependence of performance on both frequency and distance due to the sole multipath is observed, which calls for an appropriate selection of the best suitable frequency band according to the service required by the current session over the 802.11ad link
Potentials of low-complexity Rake receivers for 60 GHz UWB wireless communication systems
No full textBeside the existence of well established standards targeting the 60 GHz mmWaves band and the availability of the very first commercial products on the wireless market, there are still open research challenges at different levels of system design. Considered as the future core short-range wireless technology, 60 GHz networks are expected to revolutionize the next-generation WPAN and WLAN experience by providing reliable and energy efficient multigigabit links at lower system design complexity. In this paper, based on our empirical measurements in different measurement scenarios, carefully created to closely correspond to real usage models, we show that low-complexity UWB Rakes have the potential to be considered as serious competitor to OFDM and SC-FDE for the future 60 GHz transceiver technology. Performance evaluation is realized by semi-analytical bit error rate analyses of different Rake architectures considering high data rate modulations. We show that low-complexity Rake receiver schemes are capable to provide sufficient performance using both standard-defined 64-QAM and ultra-wideband impulse radio signaling with 64-PPM and 64-PAM. The study is realized through the spectrum from 54 to 66 GHz and the effect of the carrier frequency on the performance is also discussed
60 GHz UWB rake receivers in a realistic scenario for wireless home entertainment
No full textBy providing reliable high-capacity wireless links, the 60 GHz mmWaves band is expected to revolutionize the future wireless multimedia and home entertainment usage model, which is an inseparable part of the 5G concept. Besides the efforts within the frameworks of established standards, such as 802.15.3.c and 802.11ad, there is still lack of experimental measurements and performance evaluations in those environments that closely correspond to the different envisaged realistic application scenarios. Also, the potential of different transmission technologies at this band, besides the OFDM and SC-FDE, which are defined by the above mentioned standards, is not largely investigated in the literature. In this paper, based on UWB experimental channel impulse responses recorded in a modern residential environment, we evaluate the performance of Rake receivers to achieve high data rates (HDRs) with reasonable SNR, but still low Rake's complexity, with the purpose of meeting the QoS requirements of the wireless home entertainment use case. The bit-error rate performance evaluation of both partial and selective Rakes is applied to QPSK, 16-QAM and 64-QAM modulation schemes, defined in the existing standards. The promising results obtained in this study place the Rake receiver architecture as a valuable candidate for future 60 GHz WPANs and WLANs transceivers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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